Meso-tetra-4-actophenyl-porphyrin (TAcPPH2) was synthesized by reacting 4-acetylbenzaldehyde
with pyrrole in propionic acid, and used as a ligand for the synthesis of palladium (II)
complex (PdTAcPP). The structure of the ligand and the complex were characterized by NMR and electronic
spectroscopy. The antioxidant activity and the binding parameters of both the ligand and its complex
with superoxide anion radical .
(O2- ) were measured using cyclic voltammetry based assay. The
assays were based on the measurement of the anodic peak current density of .
generated by reduction of molecular oxygen in DMF. The complex PdTAcPP showed the highest antioxidant
activity (0.73 ± 0.01 mg/mL) which is four times higher than that of the standard antioxidant α-
tocopherol (3.04 ± 0.03 mg/mL). Binding parameters like binding constants, the ratio of binding constants
and binding free energies were also measured. The value of the binding free energy ranging from
-7.89 kJmol-1 for TAcPPH2 to -17.59 kJ.mol-1for PdTAcPP suggests an electrostatic interaction of .
with TAcPPH2 and PdTAcPP which has been found to be the dominant interaction mode. The kinetics
of the interaction reaction of the ligand and complex was quantified having second-order rate constant
values equal to 0.2 and 1.3 M-1 s-1, respectively.
Keywords: Porphyrin, Homogeneous rate constant, Cyclic voltammetry, Superoxide anion radical, Binding parameters, Antioxidant activity coefficient
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